Ab initio molecular orbital calculations of the cobalt porphine complex. I. LCAO SCF MO calculation of low-spin,high-spin,and π-ionized states of Co-porphine

Ab initio LCAO SCF MO calculations are carried out on planar Co-porphine with a basis set of roughly double zeta quality for Co and N and of single zeta quality for C and H. The net charge on Co and N and the overlap population between them are 1.78, ?0.57, and 0.06, respectively, in the ²A_1g, state, which is known to be the ground state by experiment. The bonding in this complex is thus largely ionic. The first and second calculated ionization potentials are 6.51 and 6.77 eV, respectively, and are in reasonable agreement with the observed ionization potentials of 6.44 and 6.62 eV for Ni-tetraphenylporphine. CI calculations within the framework of the ligand field theory are also performed. The calculated order of the five lowest states is ⁴B_2g ≈ ⁴E_g, ⁴A_2g, ²A_1g, ⁴E_g from below and is not in agreement with the semiempirical order of ²A_1g ≈ ⁴B_2G, ⁴A_2g, ²E_g, ⁴E_g determined by Lin.     

Ab initio study of low-lying electronic states of the FNO2 molecule

Ab initio electronic structure calculations are reported for low-lying electronic states, ¹A₁, ¹A₂, ³A₂, ¹B₁, ³B₁, ¹B₂, and ³B₂ of the FNO₂ molecule. Geometric parameters for the ground state ¹A₁ are predicted by MRSDCI calculations with a double-zeta plus polarization basis set. The vertical excitation energies for these electronic states are determined using MRSDCI/DZ+P calculations at the ground-state equilibrium conformation. The oscillator strengths and radiative lifetimes for some electronic states are calculated based on the MRSDCI wave functions. © 1993 John Wiley & Sons, Inc.     

Flux growth and structure of two compounds with the EuIn2P2 structure type,AIn2P2 (A = Ca and Sr), and a new structure type,BaIn2P2

Single crystals of the new Zintl phases AIn₂P₂ [A = Ca (calcium indium phosphide), Sr (strontium indium phosphide) and Ba (barium indium phosphide)] have been synthesized from a reactive indium flux. CaIn₂P₂ and SrIn₂P₂ are isostructural with EuIn₂P₂ and crystallize in the space group P6₃/mmc. The alkaline earth cations A are located at a site with m symmetry; In and P are located at sites with 3m symmetry. The structure type consists of layers of A²⁺ cations separated by [In₂P₂]²⁻ anions that contain [In₂P₆] eclipsed ethane‐like units that are further connected by shared P atoms. This yields a double layer of six‐membered rings in which the In—In bonds are parallel to the c axis and to one another. BaIn₂P₂ crystallizes in a new structure type in the space group P2₁/m with Z = 4, with all atoms residing on sites of mirror symmetry. The structure contains layers of Ba²⁺ cations separated by [In₂P₂]²⁻ layers of staggered [In₂P₆] units that form a mixture of four‐, five‐ and six‐membered rings. As a consequence of this more complicated layered structure, both the steric and electronic requirements of the large Ba²⁺ cation are met.     

Bildung und Struktur des iso-Tetraphosphans P(PtBu2)3: ein Molekül mit einem planaren,dreibindigen P-Atom

Formation and Structure of the iso -Tetraphosphane P(P^tBu₂)₃: a Molecule with a Planar Three-coordinated P Atom The iso-tetraphosphane P(P^tBu₂)₃ ( 1 ) was obtained by irradiating ^tBu₂P–P=P(Me)^tBu₂ ( 3 ). 1 forms hexagonal crystals (space group P6₃/m) with a = 1005,63(8), c = 1621,4(2) pm, Z = 2. The P(P^tBu₂)₃ molecules are arranged in a hexagonally close packed lattice. The four P atoms in each molecule are coplanar with P–P bond distances 219.08(4) pm and P–P–P angles 120°. The observed planar geometry is in accordance with ab initio calculations.     

Two alkali metal chlorites,LiClO2 and KClO2

The structures of tetragonal (P4₂/ncm) lithium chlorite, LiClO₂, and orthorhombic (Cmcm) potassium chlorite, KClO₂, have been determined by single‐crystal X‐ray analyses. In LiClO₂, the Li atom is at a site of symmetry, while in KClO₂, the K atom is at a site with 2/m symmetry. In both compounds, the unique Cl and O atoms are at sites with mm and m symmetry, respectively. The structure of LiClO₂ consists of layers of Li⁺ cations coordinated by ClO₂⁻ anions. In contrast, the structure of KClO₂ contains pseudo‐layers of K⁺ and ClO₂⁻ ions containing four short K—O distances. The Li⁺ and K⁺ cations are surrounded by four and eight chlorite O atoms in tetrahedral and distorted cubic coordination environments, respectively.     

A dinuclear zinc complex containing a diamond‐core geometry: [Zn2(μ2‐GueO)2(GueO)2(py)2]·0.5(toluene) (GueOH is guethol)

The title zinc alkoxide, bis(μ‐2‐ethoxyphenolato)‐κ³O¹,O²:O¹;κ³O¹:O¹,O²‐bis[(2‐ethoxyphenolato‐κ²O¹,O²)(pyridine‐κN)zinc(II)] toluene hemisolvate, [Zn₂(C₈H₉O₂)₄(C₅H₅N)₂]·0.5C₇H₈, crystallizes with two independent complex molecules located on inversion centres and one independent toluene solvent molecule disordered about an inversion centre. The Zn^II atoms are six‐coordinated in distorted octahedral geometries with O₅N donor sets. The Zn^II ions and bridging alkoxide groups are arranged in a diamond Zn₂O₂ core structure. The guetholate (2‐ethoxyphenolate) ligands adopt two different coordination modes, viz. peripheral chelating and μ₂‐bridging. Preliminary investigations of the catalytic activity of the compound in the ring‐opening polymerization of L‐lactide demonstrate rapid and efficient generation of polylactide.     

Linear Multiselenium Interactions in Dicationic Oligomers of 1,5-(Diselena)canes: Behavior of Semc σ(mcc-nee) (6≤mc≤16) Elucidated with QTAIM Dual Functional Analysis

The intrinsic dynamic and static nature m_c center-n_e electron interactions of the σ-type σ(m_cc-n_ee) were elucidated for the Se-Se interactions in dicationic oligomers of Se(CH₂CH₂CH₂)₂Se ( 1 (Se, Se)) [ n ²⁺ (Se, Se): n=1–8], especially for m_c≥6, where n ²⁺ (Se, Se: n=1–8) are abbreviated by n ²⁺ (n=1–8), respectively. QTAIM dual functional analysis (QTAIM-DFA) was applied to the interactions. Perturbed structures generated using coordinates derived from the compliance constants (C_ii) were employed for QTAIM-DFA. Each Se-*-Se in 1 ²⁺ and 2 ²⁺ has the nature of CT-TBP (trigonal bipyramidal adduct formation through CT) and Cov-w (weak covalent), respectively, which supply the starting points of the investigations. The asterisk emphasizes the existence of a bond critical point on the interaction. All Se-*-Se in 3 ²⁺ are classified by the regular closed shell (r-CS) interactions and characterized as CT-MC (molecular complex formation through CT), which are denoted as r-CS/CT-MC, except for the central interaction, of which nature is r-CS/CT-TBP. Most interactions in 4 ²⁺– 8 ²⁺ are r-CS/t-HB_wc (typical-HB with covalency) but some are pure-CS/t-HB_nc (t-HB with no covalency). The linear Se_2n²⁺ interactions in 2 ²⁺– 8 ²⁺ seem close to those without any limitations, since the nature of Se-*-Se inside and outside of (CH₂CH₂CH₂)₂ are very similar with each other. The linear Se_2n²⁺ interactions in 3 ²⁺– 8 ²⁺ are shown to be analyzed as σ(m_cc-n_ee: 6≤m_c≤16), not by the accumulated σ(3c–4e).     

A Novel Proton Transfer Self‐Associated Compound from Dipicolinic Acid and Guanidine and Its Cadmium(II) Complex: Synthesis,Characterization, Crystal Structure,and Solution Studies

A novel 1:2 proton transfer self‐associated compound LH₂ , (GH⁺)₂(pydc^2—), was synthesized from the reaction of dipicolinic acid, pydcH₂, (2, 6‐pyridinedicarboxylic acid), and guanidine hydrochloride, (GH⁺)(Cl^—). The characterization was performed using IR, ¹H and ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction. LH₂ · H₂O crystallizes in the space group C2/c of the monoclinic system and contains eight molecules per unit cell. The unit cell dimensions are: a = 26.480(5)Å, b = 8.055(2)Å, c = 14.068(3)Å. The first coordination complex (GH)₂[Cd(pydc)₂] · 2H₂O, was prepared using LH₂ and cadmium(II) iodide, and characterized by ¹H and ¹³C NMR spectroscopy and X‐ray crystallography. The crystal system is triclinic with space group P1¯ with one molecule per unit cell. The unit cell dimensions are: a = 8.5125(7)Å, b = 11.0731(8)Å, c = 13.2404(10)Å. The cadmium(II) atom is six‐coordinated with a distorted octahedral geometry. The two pydc^2— units are almost perpendicular to each other. The protonation constants of the building blocks of the pydc‐guanidine adduct, the equilibrium constants for the reaction of pydc^2— with guanidine and the stoichiometry and stability of the Cd²⁺ complex with LH₂ in aqueous solution were accomplished by potentiometric pH titration. The solution studies strongly support a self‐association between pydc^2— and GH⁺ with a stoichiometry for the Cd^II complex similar to that observed for the isolated crystalline complex. In fact, the [Cd(pydc)₂]^2— complex was found as the most abundant species in solution (> 90 %) at a pH >5.     

Ab initio studies of peroxynitrite anion-water complexes

Quantum mechanical methods have been applied to thecis-ONOO^–-H₂O,cis-ONOO^–-(H₂O)₂ andtrans- ONOO^–-H₂O complexes. Equilibrium geometries, binding energies, net atomic charges and vibrational frequencies are presented for several different arrangements. The MØller-Plessett second-order perturbation (MP2) method predicted shorter hydrogen bonds than the SCF method, but the computed Hartree-Fock (HF) binding energies are similar to counterpoise corrected MP2 values. The geometry changes of ONOO^– and water after solvation are examined. The ONOO^– and H₂O bond length changes follow typical hydrogen bond structural trends, whereas bond angles in ONOO^– are unaffected when the hydrogen bond is formed, similar to the conclusions from NO ₂ ^– -(H₂O) _n HF/6-31G studies and Monte Carlo simulations. Thecis-ONOO^–-(H₂O) _n frequencies are compared with the solution Raman spectrum and with calculations on isolated ONOO^–.     

A one‐dimensional platinum mixed‐valence complex with bridging thiocyanate S atoms: [[PtII(en)2](μ‐SCN)[PtIV(en)2](μ‐SCN)](ClO4)4 (en is ethane‐1,2‐diamine)

A new one‐dimensional platinum mixed‐valence complex with nonhalogen bridging ligands, namely catena‐poly[[[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(II)]‐μ‐thiocyanato‐κ²S:S‐[bis(ethane‐1,2‐diamine‐κ²N,N′)platinum(IV)]‐μ‐thiocyanato‐κ²S:S] tetrakis(perchlorate)], {[Pt₂(SCN)₂(C₂H₈N₂)₄](ClO₄)₄}_n, has been isolated. The Pt^II and Pt^IV atoms are located on centres of inversion and are stacked alternately, linked by the S atoms of the thiocyanate ligands, forming an infinite one‐dimensional chain. The Pt^IV—S and Pt^II...S distances are 2.3933 (10) and 3.4705 (10) Å, respectively, and the Pt^IV—S...Pt^II angle is 171.97 (4)°. The introduction of nonhalogen atoms as bridging ligands in this complex extends the chemical modifications possible for controlling the amplitude of the charge‐density wave (CDW) state in one‐dimensional mixed‐valence complexes. The structure of a discrete Pt^IV thiocyanate compound, bis(ethane‐1,2‐diamine‐κ²N,N′)bis(thiocyanato‐κS)platinum(IV) bis(perchlorate) 1.5‐hydrate, [Pt(SCN)₂(C₄H₈N₂)₂](ClO₄)₂·1.5H₂O, has monoclinic (C2) symmetry. Two S‐bound thiocyanate ligands are located in trans positions, with an S—Pt—S angle of 177.56 (3)°.     

Synthetic thermally reversible gel systems. IV

The polymerization kinetics in water of acrylylglycinamide (AG) initiated by K₂S₂O₈ was studied over the temperature range 40.0 to 60.0°C. Monomer concentration was varied from 7.8 × 10^?3 to 31.2 × 10^?3M and catalyst from 1.85 × to 11.10 × 10^?5M. The rate expression is ?d[M]/dt = R_p, = k_1.22[K₂S₂O₈]^0.5[M]^1.22, and the overall empirical rate constant, k_1.22 = 1.14 × 10¹¹e^?15,800/RT 1.^0.72 mole^?0.72 min^?1. To explain the dependence on monomer, a kinetic scheme which includes a bimolecular reaction (k₂) between monomer and initiator is suggested. The simplified expression which describes the initial rate of polymerization is: ?d[M]/dt = R_p, = k₄(2[I]/k₅)^1/2[M](k₁ + k₂[M])^1/2, where k₁, k₂, k₄ and k₅ are rate constants for S₂O₈ = decomposition, a bimolecular reaction between monomer and initiator, propagation, and termination, respectively. Individual bimolecular rate constants are expressed in liter/mole-min. The equation predicts a dependence on monomer concentration between 1.0 and 1.5 with 1.5 being approached a t high monomer concentrations. Plots of R_P²/[M]² versus [M] are linear, as predicted by the postulated reaction route and values for k₂ and k₄/k₅^1/2 were obtained from the slopes and intercepts of these plots. The temperature dependence of the bimolecular monomer-initiator reaction is k₂ = 5.19 × 10²¹e^?36,000/RT. Instead of the usual behavior, the k₄/k₅^1/2 ratio was found to decrease with temperature and the difference of activation energies, (E₄ ? E₅/2), is ?1.50 kcal. The temperature dependence of the propagation to square root of the termination rate constant ratio is k₄/k₅^1/2 = 6.16e^1500/RT. These rather unusual results may be related to the ability of AG polymers in water to form thermally reversible gels; even above the gel melting points, the polymers are considerably aggregated in solution. This would tend to make the bimolecular termination reaction more temperature dependent and also account for the high values (59–69) for the k₄/k₅^1/2 ratios. For similar temperatures, the overall rate constants for AG are approximately four times those for acrylamide.     

Hydrolysis of Methylphenyldiethoxysilane with Rare Earth Superacid Catalysts SO2− 4/TiO2/Ln3+

Abstract

An environmentally benign hydrolysis of methylphenyldiethoxysilane (MePhSi(OEt)₂) catalyzed by a rare earth superacid catalyst SO ^2? ₄ /TiO₂/Ln³⁺ has been investigated. The hydrolysis rates decrease in the order SO ^2? ₄ /TiO₂/Nd³⁺ > SO ^2? ₄ /TiO₂/Y³⁺ > SO ^2? ₄ /TiO₂/Sm³⁺ > SO ^2? ₄ /TiO₂. The hydrolysis of MePhSi(OEt)₂ is a first-order reaction with respect to the concentration of MePhSi(OEt)₂, and the hydrolysis rate constant increases with increasing temperature. The activation energy E _a and the pre-exponential factor for this hydrolysis catalyzed by SO ^2? ₄ /TiO₂/Nd³⁺ have been determined as 322.50 kJ mol^?1 and 7.12 × 10⁴¹ s^?1, respectively. The products of the hydrolysis are oligomers of polymethylphenylsiloxane. The mechanism of MePhSi(OEt)₂ hydrolysis is also discussed.     

InIII-Phthalocyanine: Darstellung,Eigenschaften und Kristallstruktur von Tetra(n-butyl)ammonium-cis-di(nitrito-O,O′)phthalocyaninato(2–)indat(III)

In^III-Phthalocyanines: Synthesis, Properties, and Crystal Structure of Tetra(n-butyl)ammonium-cis-di(nitrito-O,O')phthalocyaninato(2–)indate(III) [In(Cl)Pc^2?] reacts with (ⁿBu₄N)NO₂ in acetone yielding green-blue (ⁿBu₄N)^cis[In(NO₂)₂Pc^2?], which crystallizes in the monoclinic space group P2₁/n (No. 14). Both nitrite anions are coordinated as chelating nitrito-O,O'(NO₂) ligands to In^III in cis-geometry. Consequently In^III is octa-coordinated within a distorted “quadratic” antiprism and directed towards the Pc^2?-ligand. One of the NO₂ ligands has equivalent N? O bonds similar to free nitrite, while the other has asymmetric N? O bonds. Both (In,O,N,O) rings are approximately planar with a dihedral angle of 80°. The Pc^2? ligand is distorted in an asymmetrically convex manner. Partially overlapping pairs of Pc^2? ligands related by an inversion center form double layers, which are separated by layers containing the (ⁿBu₄N)⁺ cations. The cyclic voltammogram shows three electrode processes, which are assigned to the redox pairs: Pc^3?/Pc^2? (?0.94 V) < In^I/In^III (-0.78 V) < Pc^2?/Pc^? (0.64 V). The UV-VIS-NIR spectra and vibrational spectra are discussed.     

A Comparative Study of Platinum Di (t-butyl) (15N2)diimine and trans-[(PtCl2(N-ligand)PBu3)] complexes by 195Pt-, 31P- and 15N-NMR

¹⁹⁵Pt-, ³¹P- and ¹⁵N-NMR. data are presented for [PtCl₂ (t-Bu ¹⁵N?CH? CH?¹⁵N (t-Bu)) (η²-styrene)] ( 1 ), trans-[{PtCl₂ (PBu₃)}₂ (t-Bu ¹⁵N?CH? CH?¹⁵N (t-Bu))] ( 2 ), trans-[PtCl₂ (t-Bu ¹⁵N?CH? CH?¹⁵N (t-Bu)) (PBu₃)] ( 3 ) and various complexes of the type trans-[PtCl₂ (N-ligand) (PBu₃)]. In solution the gross structural features of 1 and 2 are shown to be in agreement with those found in the solid state; namely, 1 contains five-coordinate Pt and 2 is dinuclear. In 3 Pt is four-coordinate with only one N-atom of the diimine ligand being coordinated at ?50° in CD₂Cl₂. The NMR. data for 2 and 3 are compared with those of trans-[PtCl₂ (N-ligand) (PBu₃)] (N-ligand = pyridine, 2, 6-dimethylpyridine, (¹⁵N)-hexylamine, (¹⁵N)-t-butylamine and (¹⁵N)-aniline) and are discussed in terms of the donor and acceptor properties of the N-ligands.     

2,5‐Bis(methylthio)‐1,4‐benzo­quinone and 2‐methyl‐3‐(methylsulfonyl)benzo[b]thiophene

The structure of 2,5‐bis­(methyl­thio)‐1,4‐benzo­quinone, C₈H₈O₂S₂, is composed of an essentially planar centrosymmetric benzo­quinone substituted with two methyl­thio groups. The important bond distances are S—Csp³ 1.788 (2) and S—Csp² 1.724 (2) Å, and the two Csp²—Csp² distances are 1.447 (3) and 1.504 (3) Å, which differ significantly. There are short S?S interactions of 3.430 (1) Å and Csp²—H?O‐type contacts forming a dimeric motif with graph set R₂²(8). The structure of 2‐methyl‐3‐(methyl­sulfonyl)­benzo­[b]­thio­phene, C₁₀H₁₀O₂S₂, is composed of an essentially planar benzo­thio­phene moiety substituted with methyl and methyl­sulfonyl groups. The mean values of the important bond distances are endocyclic S—Csp² 1.734 (3), S=O 1.434 (4) and C—C_aromatic 1.389 (10) Å. The exocyclic S—Csp² and S—Csp³ distances are 1.759 (4) and 1.763 (5) Å, respectively.     

Proton transfer and isotope‐induced reaction in aniline cluster ions

The proton transfer (PT) and other intraclusters reactions occurring after electron ionization of aniline clusters (PhNH₂)_N are investigated by the time‐of‐flight mass spectrometry. The mass spectra are recorded for different expansion conditions leading to the generation of different cluster sizes. Several fragment ions are shown to originate from intracluster reactions, namely, [Ph]⁺, [PhNH₃]⁺ and [Ph–N–Ph]⁺. Reaction schemes are proposed for these ions starting with the PT process. The mass region beyond the monomer mass is dominated by cluster ions (PhNH₂)_n⁺ accompanied by satellites with ±H and +2H. In experiments with deuterated species, new fragment ions are identified. The aniline isotopomer d₅‐PhNH₂ yields the fragment ions (PhNH₂)_n?(N–Ph–NH₂)⁺. Analogical series is observed in experiments with d₇‐PhND₂, and additional fragments occur corresponding to (PhND₂)_n?(D₂N–ND–Ph–ND–ND₂)⁺ ions. The possible reaction pathways to these ions and the unusual isotope effects are discussed. Copyright © 2015 John Wiley & Sons, Ltd.     

Ab initio study of low-lying electronic states of the PF2 radical

The equilibrium geometries, excitation energies, force constants, and vibrational frequencies of the low-lying electronic states X²B₁, ²A₁, ²B₂, and ²A₂ of the PF₂ radical have been calculated at the MRSDCI level with a double zeta plus polarization basis set. Our calculated geometry, force constants, and vibrational frequencies for the X²B₁ state are in good agreement with experimental data. The electronic transition moments, oscillator strengths for the ²A₁ → X²B₁ and ²A₂ → X²B₁ transitions, and radiative lifetimes for the ²A₁ and ²A₂ states are calculated based on the MRSDCI wave functions. © 1994 by John Wiley & Sons, Inc.     

Darstellung,Kristallstrukturen, Schwingungsspektren und Normalkoordinatenanalyse von cis‐ und trans‐(n‐Bu4N)2[PtF2(ox)2] und (n‐Bu4N)2[PtF4(ox)]

Synthesis, Crystal Structure, Vibrational Spectra, and Normal Coordinate Analysis of cis‐ and trans‐(n‐Bu₄N)₂[PtF₂(ox)₂] and (n‐Bu₄N)₂[PtF₄(ox)] By treatment of trans‐(n‐Bu₄N)₂[PtCl₂(ox)₂] and (n‐Bu₄N)₂[PtCl₄(ox)] with XeF₂ in propylene carbonate cis‐ and trans‐(n‐Bu₄N)₂[PtF₂(ox)₂] ( 1 , 2 ) and (n‐Bu₄N)₂[PtF₄(ox)] ( 3 ) are formed which have been isolated by ion exchange chromatography on diethylaminoethyl cellulose. The crystal structure of trans(n‐Bu₄N)₂[PtF₂(ox)₂] ( 2 ) (tetragonal, space group P4₂/n, a = 15.5489(9), b = 15.5489(9), c = 17.835(1)Å, Z = 4) und Cs₂[PtF₄(ox)] ( 3 ) (monoclinic, space group C2/m, a = 14.5261(7), b = 6.2719(4), c = 9.6966(9)Å, β = 90.216(8)°, Z = 4) reveal complex anions with nearly D_2h and C_2v point symmetry. The average bond lengths in the symmetrical coordinated axes are Pt—F = 1.93 ( 2 , 3 ) and Pt—O = 1.987 ( 2 ) and in the F^•—Pt—O′‐axes Pt—F^• = 1.957 and Pt—O′ = 1.977Å ( 3 ). The oxalato ligands are nearly planar with a maximum displacement of the ring atoms of 0.05 ( 2 ) und 0.01Å ( 3 ) to the calculated best planes. In the vibrational spectra the symmetric and antisymmetric PtF stretching vibrations are observed at 583 and 586 ( 2 ) and 576 and 568 cm^—1 ( 3 ). The PtF^• modes appear at 565 and 562 ( 1 ) and 560 cm^—1 ( 3 ). The PtO and PtO′ stretching vibrations are coupled with internal modes of the oxalato ligands and appear in the range of 400—800 cm^—1. Based on the molecular parameters of the X‐ray determinations ( 2 , 3 ) and estimated data ( 1 ) the IR and Raman spectra are assigned by normal coordinate analysis. The valence force constants are f_d(PtF) = 3.55 ( 2 ) and 3.38 ( 3 ), f_d(PtF^•) = 3.23 ( 1 ) and 3.20 ( 3 ), f_d(PtO) = 2.65 ( 1 ) and 2.84 ( 2 ) and f_d(PtO′) = 2.97 ( 1 ) and 3.00 mdyn/Å ( 3 ). Taking into account increments of the trans influence a good agreement between observed and calculated frequencies is achieved. The NMR shifts are δ(¹⁹⁵Pt) = 8485 ( 1 ), 8597 ( 2 ) and 10048 ppm ( 3 ), δ(¹⁹F) = —350 ( 2 ) and —352 ( 3 ) and δ(¹⁹F^•) = —323 ( 1 ) and —326 ppm ( 3 ) with the coupling constants ¹J(PtF) = 1784 ( 2 ) and 1864 ( 3 ) and ¹J(PtF^•) = 1525 ( 1 ) and 1638 Hz ( 3 ).     

New Homoleptic Rare Earth 3,5‐Diphenylpyrazolates and 3,5‐Di‐tert‐butylpyrazolates and a Noteworthy Structural Discontinuity

Direct thermally induced reactions between rare earth metals (Ln = Y,Ce, Dy, Ho, and Er) activated by Hg metal and 3,5‐diphenylpyrazole (Ph₂pzH) or 3,5‐di‐tert‐butylpyrazole (tBu₂pzH) yielded either homoleptic complexes [Ln_n(R₂pz)_3n] or a heteroleptic complex [Ln(Ph₂pz)₃(Ph₂pzH)₂] From Ph₂pzH, [Ce₃(Ph₂pz)₉], [Dy₂(Ph₂pz)₆], [Ho₂(Ph₂pz)₆], and [Y(Ph₂pz)₃(Ph₂pzH)₂] were isolated. The first has a bowed trinuclear Ce₃ backbone with two η² pyrazolate ligands on the terminal metal atoms and one on the middle, and bridging by both μ‐η²:η² and μ‐η²:η⁵ ligands between the terminal and the central Ce atoms. Although both the Dy and Ho complexes are dinuclear, the former has the rare μ‐η²:η¹ bridging whilst the latter has μ‐η²:η² bridging. Thus the dysprosium complex is seven‐coordinate and the holmium is eight‐coordinate, in contrast to any correlation with Ln³⁺ ionic radii, and the series has a remarkable structural discontinuity. The heteroleptic Y complex is eight coordinate with three chelating Ph₂pz and two transoid unidentate Ph₂pzH ligands. From tBu₂pzH, dimeric [Ln₂(tBu₂pz)₄] (Ln = Ce, Er) were isolated and are isomorphous with eight coordinate Ln atoms ligated by two chelating terminal tBu₂pz and two μ‐η²:η² tBu₂pz donor groups. They are also isomorphous with previously reported La, Nd, Yb, and Lu complexes.     

Ligand exchange reactions of fac -(dihapto-[60]fullerene) (dihapto-1,2- bis -(diphenylphosphino)ethane tricarbonyl chromium(0)

The complex fac-(η²-C₆₀)(η²-dppe)Cr(CO)₃ (dppe?=?1,2-bis(diphenylphosphino)ethane and C₆₀?=?[60]fullerene) reacts with piperidine (pip) to produce fac-(η²-C₆₀)(η¹-pip)₂Cr(CO)₃. The reactions are first order with respect to [?fac-(η²-C₆₀)(η²-dppe)Cr(CO)₃] under flooding conditions where [pip]???[?fac-(η²-C₆₀)(η²-dppe)Cr(CO)₃]. The pseudo-first order rate constant values (k _obsd) are [pip]-dependent. Curved (upward) plots of k _obsd versus [pip] and linear plots of k _obsd versus [pip]² indicate that the piperidine-assisted dppe displacement from fac-(η²-C₆₀) (η²-dppe)Cr(CO)₃ is second order with respect to [pip]. The proposed mechanism involves a [60]fullerene-stabilized intermediate.